1. Field of the Invention
The present invention relates to a contact structure of a BGA type IC package or a PGA type IC package with an IC socket.
2. Brief Description of the Prior Art
Referring to FIG. 1A to FIG. 1C, a BGA type IC package includes a number of semispherical terminals 2 below an IC package main body 1 as shown in FIG. 1A or it includes a number of spherical terminals 2 below an IC package main body 1 as shown in FIG. 1B. In addition, a PGA type IC package includes a number of cylindrical terminal 2 which are projected from the lower surface of an IC package main body 1 as shown in FIG. 2A and FIG. 2B.
Conventionally, the contact structures employed for the BGA type IC package or the PGA type IC socket have included a contact structure for allowing a resilient contact piece of a contact to come in pressure contact with one side surface of a spherical surface of the spherical type or cylindrical type terminal 2 and a contact structure for holding the spherical type or cylindrical type terminal 2 with a pair of resilient contact pieces in the clamped state so as to allow the resilient contact piece to come in pressure contact with the opposing two side surfaces.
There is a tendency toward terminals 2 being arranged at a shorter pitch and the contact area being increasingly restricted. Also, the aforementioned contact structure assures that the position of the terminal is restricted in the direction in which the resilient contact piece comes into pressure contact, but the position of the terminal is not restricted in other directions. Accordingly, there appears a problem that the positions of the terminals may deviate in such other directions with the result that it is difficult to correctly maintain the contacted state. Thus, it is difficult to cope with the tendency toward terminals being arranged with a shorter pitch.
As means for preventing the foregoing positional deviation, there is practiced a method of bringing a resilient contact piece into pressure contact with a terminal while the terminal is surrounded by the resilient contact piece at three or more points. This method can solve the problem of positional deviation but in consideration of the background that spherical type terminals and cylindrical type terminals are currently arranged at a very small pitch of 1.27 mm or less, it becomes very difficult from the viewpoint of the required space to dispose three or more resilient contact pieces around each terminal. Moreover, it becomes difficult to precisely work the resilient contact piece itself.